This study aims to investigate the link between early biosocial risk factors and childhood externalizing behavior problems. Specifically, the study will examine how prenatal health factors interact with postnatal psychosocial risk factors in predisposing to later externalizing behavior. The specific aims are to: (1) assess the direct effect of prenatal biological and postnatal psychosocial risk factors on childhood externalizing behavior; (2) examine the interactive effect of biological and psychosocial risk factors on childhood externalizing behavior; (3) test what factors mediate the above direct and interactive effects of biological/social risk factors on childhood externalizing behavior; (4) identify the specific components of biological and social risk factors which give rise to childhood externalizing behavior; (5) test the relationship between internalizing behavior in relation to the above risk and mediating factors in predisposing to childhood internalizing behavior. Prenatal biological risk factors include maternal smoking during pregnancy, and pregnancy/birth complications. Postnatal psychosocial risk factors include parenting, child rearing disagreements, domestic violence, and home environment. Further, the mediating role of cognitive ability, and temperament, will also be explored. Hypotheses will be tested in the context of an ongoing prospective longitudinal study of approximately 600 three-year-old male and female children using structural equation modeling. By attempting to further establish the early, modifiable health risk factors for externalizing behavior, and by examining a biosocial perspective on antisocial behavior, the proposed study aims to illustrate how the Nursing profession can potentially impact this significant societal problem as well as better inform future prevention programs.